Electronic, optoelectronic, microwave, RF and electrical devices are typically mounted on substrates that provide support and act to remove heat from the device. The main requirements for such substrates are that they possess sufficient dielectric strength and a good thermal conductivity. A substrate on which such a device can be mounted is known as an insulated metal substrate (IMS).
Insulated metal substrates (IMSs) are typically used for electronic devices that generate high specific heat energy, for example in high power electronics, solid-state lighting, telecommunication and concentrated photovoltaic applications. IMSs usually comprise a metal sheet base covered from one side or two sides by an insulating layer of dielectric material, which may be polymeric, for example resin, fluoropolymer, polyimide and their composites charged with thermally conductive ceramic powders, etc. Such sheet IMS often named as Metal Core Printed Circuit Boards (MC PCB) then are usually attached to a heat think through a layer of thermal interface material.
In order to reduce thermal path a dielectric layer can be formed directly on a heat sink by use of anodising as described in GB 2162694, or Plasma Electrolytic Oxidation (PEO) as described in US Pat. 2008257585A1.
An IMS, which may be a metal board, a heat sink, a device body or supporting frame, requires dielectric material to have a high dielectric strength to secure electric insulation from circuitry of the device, thereby avoiding or preventing the device from short-circuiting. Thermal conductivity of dielectric material is also required to dissipate heat generated by the device, which negatively effects performance, reliability and the lifetime of the device. In general, an increased dielectric strength enables the IMS to have a thinner insulating layer, which is reducing IMS thermal resistance (with the same thermal conductivity of insulating material).
For RF and microwave applications it may be beneficial that an IMS comprises a dielectric material that has a high dielectric constant.
It is an aim of the invention to provide an IMS having improved properties.